283. Targeted Delivery of C/EBPα-Small Activation RNA (saRNA) by RNA Aptamer Inhibits the Growth of Pancreatic Ductal Adenocarcinoma (PDAC) In Vivo

Transcriptional factor C/EBPα (CCAAT/enhancer-binding protein-a) is downregulated and silenced in pancreatic ductal adenocarcinoma (PDAC). In this study, we tested the feasibility of targeting promoter regions of transcriptional factor C/EBPα to induce transcriptional activation by small activation RNA (saRNA) for cancer therapeutics in PDAC. C/EBPα is known to up-regulate p21, a strong inhibitor of cell proliferation. C/EBPα-saRNA inhibited cell proliferation in PDAC. For the targeted delivery into cells, small structured single-stranded RNAs known as aptamers, recognizing targets specifically, were employed for the effective delivering vehicles. 2’-fluropyrimidine RNA aptamers (2’F-RNA) were selected to acquire nuclease resistance based on the whole cell SELEX. The cell internalization was evaluated through flow cytometry and confocal microscopy. The selected 2’F-RNA aptamers got internalized into a variety of pancreatic cancer cell lines. Human pancreatic cancer specimen histopathology and cell binding assays indicated that they recognized cancer cells specifically, not to normal cells. The conjugates, aptamer with C/EBPα-saRNA, were constructed for the targeted delivery. The conjugates escaped endosome and localized in nuclear. The conjugates of aptamer with C/EBPα-saRNA inhibited cell proliferation and upregulated gene expression. Xenograft mice model was used to test tumor cell growth inhibition in vivo throughout the transcriptional activation of C/EBPα. The conjugates of aptamer with C/EBPα-saRNA reduced tumor burden significantly in vivo, showing its anti-tumor effects. The aptamer target expressed on cell membrane was identified mitochondrial Hsp70. For the first time, results from these studies provide a new therapeutics strategy through transcriptional activation of C/EBPα by aptamer mediation induce anti-tumor effects in pancreatic cancer.